"If you are using an ATM and your card sticks, there is probably a skimmer," the warning said.

Card skimmers have been found on gas pumps at several stations in the state in recent months, most recently at a station in Oak Creek. The technology allows a criminal to capture the data on a credit or ATM card and use it to make fraudulent cards.

Anyone who suspects that a card skimmer exists on a device should contact authorities. Greenfield police can be reached at 414-761-5301.